Laboratory centrifuges have a rotor, which has receptacles distributed over its circumference. Into these receptacles vessels can be inserted in which substances to be treated by centrifuging are stored. To cause the rotor with the vessels with the substances accommodated in the receptacles to rotate with a rotation required for the centrifuging, an output element of the rotor is coupled with a driving element of the laboratory centrifuge, usually formed by a driving shaft, driven by a motor. In this context the coupling device serves for axially securing the output element on the driving element and therefore serves for axially securing the rotor on the driven driving shaft. It is possible that the coupling device also serves for a form-locking transmission of the driving moment from the driving shaft to the rotor. Preferably, the transmission of the driving moment is achieved through a friction-locking of coupling surfaces, where the contact force of the coupling surfaces may be dependent on a weight of the rotor and a force component of a coupling force. High demands have to be made to the operational safety of the coupling device especially due to aerodynamic effects resulting from high revolution speeds, the high centrifugal forces, gyro effects at substantive impacts upon the laboratory centrifuge and the like.
In laboratory operation of the laboratory centrifuge as intended, repeated mounting and demounting of the rotor is necessary to be able to successively examine a plurality of vessels with substances to be centrifuged with the same rotor or different rotors. In this context it has emerged that in view of the effort of manual operation and the time consumption connected therewith, but also in view of the operational safety, the use of manually operated coupling devices may be disadvantageous. For this reason coupling devices operated by centrifugal force are used in which the output element of the rotor is merely set onto the driving element of the laboratory centrifuge driven by the motor. While in the beginning only a friction locking between driving element and output element due to the weight of the rotor causes the coupling between the driving element and the output element, with increasing rotational speed of the rotor due to the centrifugal force the coupling force of the coupling device operated by centrifugal force increases. The larger the rotational speed is, the larger the coupling force generated by the centrifugal force is automatically. While centrifuging is being ended, the driving shaft can be braked, in which way the coupling device operated by centrifugal force is unlocked automatically. (A manually-operated coupling device may be employed in addition to such a coupling device actuated by centrifugal force.)
From U.S. Pat. No. 6,063,018 a laboratory centrifuge is known in which a driving element with a driving surface in the shape of a truncated cone is driven by a motor. The rotor has a corresponding inner friction surface in the shape of a truncated cone with which the rotor due to its weight is pressed onto the friction surface of the driving element having the shape of a truncated cone. When the driving motion of the driving element begins, the friction force between the friction surfaces results in a transmission of the rotational motion to the rotor. In a transverse plane of the driving element, distributed on the circumference and lying opposite of each other, two coupling levers are supported in such a way as to be pivotable outwards due to the centrifugal force. Coupling surfaces of the coupling levers inclined with respect to the transverse direction of the driving element are pressed onto corresponding opposite coupling surfaces of the rotor due to the centrifugal force. In this way on the one hand a form-locking axial securing of the rotor on the driving element is caused. Due to the inclination of the coupling surfaces and the opposite coupling surfaces, the centrifugal force leads to an axial force component dependent on the speed of rotation, which increases the contact force of the friction surfaces in the shape of a truncated cone towards each other with increasing speed of rotation. After positioning the rotor onto the driving element, springs already press the coupling levers radially outwards, in which way even without rotation a locking of the rotor is achieved. For an unlocking of the rotor a manual actuation of a button is necessary, which leads to a motion of the coupling levers radially inwards with an accompanying unlocking of the coupling device.
A corresponding solution is known from WO 2010/025922 A1 (corresponding to U.S. Pat. No. 8,678,987 B2).
DE 10 2012 011 531 A1 (corresponding to US 2013/0331253 A1) discloses a driving head for a laboratory centrifuge, in which a coupling device is employed the effect of which is at least augmented by centrifugal force. The driving head comprises a motor-driven base body, to which during operation of the laboratory centrifuge a hub connected to a rotor of the laboratory centrifuge is detachably connected. On the hub there are at least two coupling levers different from each other, which each are pivotable around an axis parallel to the rotational axis of the laboratory centrifuge. In a standstill of the centrifuge, the coupling levers are pivoted into the base body or are under an outward bias caused by a spring. The hub is slid onto the base body until suitably formed undercuts in the hub each lie opposite to the coupling levers. At rotation of the laboratory centrifuge, the eccentrically arranged coupling levers due to the centrifugal force pivot outwards around their pivot axis and into the corresponding undercut in the hub. The undercuts at the lower edge, which is in contact with the coupling lever, are formed in such a way that with a pivoting movement of the coupling levers the hub is pressed in an axial direction onto the base body and connected with it in a friction-locking way.
While for the aforementioned embodiments the coupling lever is supported on the driving element and pivoted in a transverse plane of the driving element, WO 2011/001729 A1 discloses an embodiment in which the coupling lever is supported on the output element of the rotor for being pivoted in a plane including the rotational axis. Due to the centrifugal force the coupling lever is pivoted radially outwards, where it engages in an undercut of a front-facing recess of a driving shaft.
The embodiments known from U.S. Pat. No. 6,063,018, WO 2010/025922 A1 and WO 2011/001729 A1 are based on a pivoting of a locking catch of a coupling lever in outward direction due to the centrifugal force. However, an inwards locking motion of a locking catch of a coupling lever could also be of interest, for instance to lock a coupling lever supported on the rotor with a groove of a driving shaft. For the “deflection” of the centrifugal force required to exert a bias in radial inward direction onto the locking catch, locking levers are used, at which the center of gravitation is located radially outwards of a pivoting axis of the locking lever, while the locking catch of the locking lever is located radially inwards from the pivoting axis. Examples of such embodiments may be taken from the documents WO 2011/054901 A1 (corresponding to US 2013/0203581 A1), WO 2011/054906 A1 (corresponding to US 013/0237399 A1) and WO 2012/059151 A1 (corresponding to U.S. Pat. No. 8,852,070 B2).
With the novel coupling device actuated by centrifugal force and laboratory centrifuge with such a coupling device actuated by centrifugal force, it is possible to achieve an alternative design of a coupling device actuated by centrifugal force or a laboratory centrifuge with such a coupling device actuated by centrifugal force, respectively. The novel coupling device or laboratory centrifuge might be improved especially with regard to                the building effort,        the operational strength and/or        the coupling characteristic.        